Community responses to fine-scale environmental conditions: Ferns alpha and beta diversity along Brazilian Atlantic forest remnants

Understanding how local environmental factors affect communities and compositional patterns are crucial to biodiversity conservation, especially in environments that were severally affected by anthropic actions. We analyzed the effects of fine-scale local environmental conditions on alpha and beta diversity of fern communities in three Atlantic forest areas and investigated the mechanisms underlying fern community responses. We sampled ferns and collected local environmental variables in 22 plots in three Atlantic forest areas and used multi-model inferences to identify the relationship between community diversity and composition and local environmental factors. We also applied multivariate analyses to verify whether community composition is constrained by local environmental factors. Finally, we analyzed beta-diversity (dissimilarity in species composition) patterns between and within forest areas and identified the contribution of turnover and nestedness to observed beta-diversity patterns. At the local scale, fern diversity was positively and strongly affected by fine-scale variations in nutrient availability and negatively influenced by soil acidity. Meanwhile, changes in community composition were also related to fine-scale variations in nutrient availability and soil rock coverage. Beta-diversity within forest areas (local scale) was as high as between forest areas (regional scale), a pattern that was virtually driven by species turnover at both scales of analysis. Our results highlight a prominent role of environmental filtering in regulating fine-scale local fern community diversity and composition, to such an extent that fine-scale local variation in species composition is as high as between spatially and climatically distant forest areas.